I bought a bunch of duplos from the thrift store and inside there was not Just duplos but also mega bloks. I was able to separate most of them but there are a few that I just cannot tell which is which. They have a logo in the middle of the stack but its a picture rather than a word. I'm trying to find anything online but am having no luck. The logo almost looks like a smiling face or an umbrella with 2 dots on each side.

I tried too but it says I need a reputation of 10 so it will be a while before I can add one.
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Lisa AJul 23 '13 at 14:00

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I uploaded an image of blocks with the mystery umbrella/smiley/anchor(?) logo. The blocks don't have any other indication on them of manufacturer, although based on the collection they were found in, I would estimate they were sold in the mid-1980s.
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oddToddJul 24 '13 at 4:02

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Yes, that's the logo! As for an information I'm still looking but coming up with nothing. They don't feel like a megablok does they feel more like a duplo but that's about all I know about them.
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Lisa AJul 25 '13 at 13:29

All Duplo and LEGO bricks have the LEGO logo (the logo is just the word LEGO) on the brick somewhere, usually on a stud. Megabloks always have blank studs and slightly offset colors compared to LEGO or Duplo bricks.

Although the logo on the "umbrella-bricks" you have are not Megablock, they are not Duplo either. Duplo always have the LEGO logo somewhere, and the studs are hollow. The hollow studs make them compatible with standard Lego bricks that are at least size 2x2, since the cylinder inside the Lego brick fits perfectly inside the hollow Duplo stud. See the locomotive on this image where it has some 2x4 Lego bricks on Duplo bricks:

Also see this answer on another post for more details on Duplo piece information.